A vulnerability in the self-service portal of Cisco Duo could allow an unauthenticated, remote attacker to inject arbitrary commands into emails that are sent by the service. This vulnerability is due to insufficient input validation. An attacker could exploit this vulnerability by injecting arbitrary commands into a portion of an email that is sent by the service. A successful exploit could allow the attacker to send emails that contain malicious content to unsuspecting users.
The product constructs all or part of a command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended command when it is sent to a downstream component.